Selective fat removal using photothermal heating

ABSTRACT

A system and method are provided for minimally-invasive selective fat removal from a target area by injecting the area with a solution of photo-absorbing nanoparticles and irradiating the injected area with a beam of near infrared (NIR) light. The NIR emission wavelength excites the nanoparticles to melt fat within the target area so that the liquefied fat can be aspirated from the target area. The nanoparticles may be gold nanorods having aspect ratios selected to produce surface plasmon resonance when irradiated with NIR light around 800 nm.

RELATED APPLICATIONS

This application is continuation-in-part of application Ser. No.14/464,629, filed Aug. 20, 2014, which is a continuation of applicationSer. No. 14/379,488, filed Aug. 18, 2014, which is a 371 national stagefiling of International Application No. PCT/US2013/040219, filed May 8,2013, which claims the benefit of the priority of Application No.61/644,328, filed May 8, 2012, which is incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

The invention relates to a system, kit and method for reduction of fattytissue in the body, and more particularly to removal of fatty tissueusing near infrared laser light to irradiate nanoparticles injected intothe tissue.

BACKGROUND OF THE INVENTION

Liposuction evolved from work in the late 1960s from surgeons in Europeusing primitive curettage techniques which were largely ignored, as theyachieved irregular results with significant morbidity and bleeding.Modern liposuction first burst on the scene in a presentation by theFrench surgeon, Dr Yves-Gerard Illouz, in 1982. The “Illouz Method”featured a technique of suction-assisted lipolysis after tumesing orinfusing fluid into tissues using blunt cannulas and high-vacuum suctionand demonstrated both reproducible good results and low morbidity.During the 1980s, many United States surgeons experimented withliposuction, developing variations, and achieving mixed results. Mostcommonly, liposuction is performed on the abdomen and thighs in women,and the abdomen and flanks in men. According to the most recentstatistics by the American Society for Aesthetic Plastic Surgery,liposuction, including conventional suction-assisted lipectomy (SAL),ultrasound-assisted liposuction (UAL), and laser-assisted liposuction(LAL), is the most common aesthetic procedure performed by plasticsurgeons in the United States. However, these procedures are oftenassociated with secondary complications such as contour deformities,irregular lumpy appearance, and excess skin, leading to patientdissatisfaction.

Traditional liposuction relies on two techniques. The first techniqueemploys a sharp, relatively large diameter (3 mm-5 mm) cannula that ismanually manipulated to mechanically break fat down and while applyingsuction to remove the separated fat. A variation of this vacuum assistedtechnique is a mechanically powered cannula that reduces the surgeon'sfatigue during large surface area liposuction procedures.

The second technique utilizes ultrasonic waves via a vibrating cannula,this technique is mechanical in its nature and significantly reduces thesurgeon's fatigue factor. This technique induces the same or worsemechanical trauma to the tissues. Both techniques require significantamounts of fluid, known as a “tumescent solution,” to be injected intothe body to emulsify the fat, facilitating the removal of large volumesof fat while reducing blood loss and delivering a local anesthetic(lidocaine) to provide post-operative pain relief. While generally safe,lidocaine can be toxic, leading to serious complications, and evendeath.

A problem with the probes used in existing liposuction procedures is thegeneration of significant amounts of heat at the distal tip of theprobe, which can exceed the temperature required for melting the fattytissue. This excess heat can result in burning of tissue, damagingmuscles or blood vessels, and even penetrating membranes such as theskin or the peritoneum that covers most of the intra-abdominal organs.

Alternative methods have been disclosed which exploit laser energy toremove unwanted fat, known as laser-assisted liposuction (LAL). CurrentFDA-approved technologies for LAL rely predominantly on wavelengthsaround or beyond 1000 nm, where water absorbs and emits heat. As aresult, these methods require the insertion of laser probes into thesubcutaneous tissue to liquefy small volumes of fat. Because of thepoint source nature of the heating device, results are not uniform, andsurrounding subcutaneous tissue, such as muscle and fibrous connectivetissues, may also be heated. Further, because such systems rely onendogenous chromophores such as water or hemoglobin, their concentrationis fixed.

U.S. Pat. Nos. 6,605,080 and 7,060,061, both issued to Altshuler, et al.represent an alternative approach in which laser energy is externallyapplied to the skin to heat and melt fat tissue in epidermis andsubcutaneous layers below. These patents disclose the use of near- tomid-infrared radiation wavelengths that are preferentially absorbed bylipid cells to heat-liquefy fat cells, after which the lipid pool may beremoved from the subcutaneous area by aspiration. The need to fine-tunethe laser wavelength for preferential absorption by the lipid cells, aswell as the considerable heat generation that results from thetechniques, e.g., up to 70° C., at or in the fat tissue, require use ofa cooling mechanism to prevent skin damage or permanent scarring. Thesemethods present other limitations and potential adverse thermal effectson tissue above the lipid-rich tissue under treatment, includingblistering, peeling, and depigmentation.

U.S. Pat. No. 8,357,146 of Hennings discloses a LAL device and method inwhich wavelengths of pulsed laser radiation that are preferentiallyabsorbed by lipid cells are applied directly to the tissue by insertinga fiber optic probe into the target area. As in Altschuler's method, thedirect absorption of the laser energy heats the fat, however, thisheating is augmented by a coating on the optical fiber that absorbs thelaser energy and acts as a hot tip, or “char”, to ablate and disrupttissue. This high temperature char creates a risk of accidental damageto surrounding tissue.

U.S. Pat. No. 8,430,919 of Bornstein discloses a lipolysis method inwhich the skin over the target site is optically irradiated with twodifferent wavelengths of light, one in the near infrared (NIR) region,the other in the infrared range, to modulate biochemical processes ofadipocytes in the target site. In order to achieve the desired degree offat removal, the duration of the treatment must be relatively long, fromone to two hours, during which the patient must remain virtuallymotionless. Unless a sedative or general anesthesia has beenadministered to calm the patient, physical and psychological discomfortcan ensue.

NIR (700-950 nm) is preferable to other types of light for therapeuticuse in biological systems because NIR light can pass through blood andtissue to depths of several inches. However, very few organicchromophores absorb in this region, and even fewer are capable ofconverting the absorbed energy into a chemical or thermal response thatcan be used to trigger drug release. A few years ago, goldnanostructures (shells, particles, rods, and cages) emerged as usefulagents for photothermal therapy after they were shown to have strongabsorption in the NIR region (four to five times higher thanconventional photo-absorbing dyes) as well as tunable opticalresonances. The strong absorption enables effective laser therapy atrelatively low laser energies, rendering such therapy methods minimallyinvasive.

Laser photothermal therapy of cancer with the use of gold nanoparticlesimmunotargeted to molecular markers has been reported as being effectiveto selectively kill cancer cells at lower laser powers than those neededto kill healthy cells. (X. Huang, et al., “Determination of the MinimumTemperature Required for Selective Photothermal Destruction of CancerCells with the Use of Immunotargeted Gold Nanoparticles”, Photochemistryand Photobiology, 2006, 82:412-417.) Gold nanoparticles absorb lightefficiently in the visible region due to coherent oscillations of metalconduction band electrons in strong resonance with visible frequenciesof light, a phenomenon known as “surface plasmon resonance” or “SPR”.Photoexcitation of metal nanostructures results in the formation of aheated electron gas that cools rapidly, e.g., within 1 ps, by exchangingenergy with the nanoparticle lattice. The nanoparticle lattice, in turn,rapidly exchanges energy with the surrounding medium on the timescale of100 ps, causing localized heating. This rapid energy conversion anddissipation can be achieved by using light radiation with a frequencythat strongly overlaps the nanoparticle absorption band.

U.S. Patent Publication 2012/0059307 of Harris et al. discloses a methodof selective thermomodulation in tissue that applies nanoparticles to atarget tissue region that is then irradiated with laser light to inducethermal damage to destroy or remove the tissue by ablation. Ablationinvolves the cutting or removal of tissue by fracture of chemical bondsthrough phase transitions consisting of vaporization, molecularfragmentation, and/or void formation, i.e., a violent, destructiveprocess. (See, e.g., A. Vogel and V. Venugopalan, “Mechanisms of PulsedLaser Ablation of Biological Tissues”, Chem. Rev. 2003, 103, 577-644.)Harris' et al.'s target tissue includes hair follicles, sebaceousglands, and unwanted or diseased vasculature, where destruction(necrosis or apoptosis) of the target tissue is the goal. However, forapplications where actual destruction of the tissue is not desirable,this approach is not appropriate.

The conditions for irradiation as well as the nanoparticlecharacteristics are critical for obtaining the necessary control forproviding effective treatment while avoiding tissue damage. Nanorodsexhibit cylindrical symmetry, and simple changes in particle symmetrycan significantly alter SPR characteristics. The NIR absorption maximumof metal nanostructures can be modulated by changing their size, shapeand aggregation. GNRs have two plasmon absorption peaks, exhibitingtransverse and longitudinal surface plasmon resonances that correspondto electron oscillations perpendicular and parallel to the rod lengthdirection, respectively. The longitudinal surface plasmon wavelengthsare tunable from the visible to infrared regions. The effectiveness ofGNRs as photothermal therapeutic agents is strongly dependent on theirscattering and absorption cross-sections—large absorption cross sectionswith small scattering losses allow for photothermal therapy with aminimal laser dosage. In addition, the longitudinal surface plasmonwavelengths of GNRs are preferably within the spectral range of 650-900nm. Light irradiation in this region can penetrate more deeply intotissues and cause less photodamage than UV-visible irradiation.Therefore, the ability to tailor both scattering and absorption of GNRswith different longitudinal surface plasmon wavelengths is important fortherapeutic applications.

BRIEF SUMMARY

In an exemplary embodiment, the apparatus and method of the presentinvention combines near infrared (NIR) light exposure and a solution ofgold nanorods (GNRs) that may be injected into the treatment target inorder to selectively and gently heat fat in the target area. The lowpower NIR light harmlessly penetrates the skin and overlying tissue tobe absorbed only by the GNRs. The excited GNRs generate heat, meltingthe fat and tightening the skin. The liquefied melted fat can be removedwith a syringe or fine cannula.

According to an embodiment of the invention, a GNR solution energized byNIR laser exposure heats adipose tissue by surface plasmon resonance(SPR). The wavelength absorbed can be tuned by altering particle shape,size, geometry, and aspect ratio. This absorption causes gold electronsto oscillate with the frequency of the electromagnetic field, generatingheat with extremely high efficiency. Photothermal conversion through SPRallows for rapid but controlled localized heating that is more selectivethan other methods of heating, and is thus suitable for heating of softtissue. Photothermal conversion through SPR takes advantage of thedifference in thermal relaxation rates between fat and surroundingtissues to allow selective photothermolysis. Because fat has a lowerthermal conductivity (0.631 W m⁻¹ K⁻¹ vs. 0.23 W m⁻¹ K⁻¹), (13, 14) aswell as a lower specific heat capacity (4.18 kJ g⁻¹ K⁻¹ vs. 2.3 kJ g⁻¹K⁻¹ ) than water, it heats faster and dissipates heat more slowly,enhancing the selectivity of heating enabled by injection of the GNRsolution into the adipose layer. Heating by this mechanism softens andloosens adipose tissue, facilitating removal with minimal trauma. Onlysurgeon-defined regions, where the GNR solution is infused, absorb laserenergy, minimizing the potential for damage to surrounding tissues.

In one aspect of the invention, a system is provided forminimally-invasive removal of fat within a target area, including asolution of photo-absorbing nanoparticles; means for injecting thesolution into the target area; a near infrared light source fordelivering a beam of light to the target area; at least one beamadjusting optical element for controlling focus and beam size within thetarget area; a system controller for providing control signals to theinfrared light source, wherein the control signals comprise selection ofan emission wavelength, an emission intensity and an exposure duration,and wherein the emission wavelength is adapted to excite thenanoparticles to melt fat within the target area; and means forextracting melted fat from the target area. In a preferred embodiment,the nanoparticles are biocompatible, and photo-absorption in thenanoparticles is mediated by surface plasmon resonance. Thenanoparticles may be selected to absorb in the near infrared range(700-900 nm) and in the preferred embodiment are gold nanorods. The goldnanorods may have an aspect ratio in the range of 1:3-1:5, with an axialdiameter of approximately 10 nm and a longitudinal diameter in the rangeof 9-50 nm. The gold nanorods may be suspended in water at aconcentration of around 3×10¹¹−3×10¹² GNR/mL. The near infrared lightsource may be a NIR laser having tunable power and/or wavelength, andfurther comprising beam adjusting optical means for control of beam sizeat the target area and may emit light within the wavelength range of 600nm to 950 nm, more preferably in the range of 700 nm to 900 nm, and mostpreferably around 800 nm.

In another aspect of the invention, a photothermal method is providedfor in vivo fat removal by melting the fat using the system thatincludes a solution of photo-absorbing nanoparticles; means forinjecting the solution into the target area; a near infrared lightsource for delivering a beam of light to the target area; at least onebeam adjusting optical element for controlling focus and beam sizewithin the target area; a system controller for providing controlsignals to the infrared light source, wherein the control signalscomprise selection of an emission wavelength, an emission intensity andan exposure duration, and wherein the emission wavelength is adapted toexcite the nanoparticles to melt fat within the target area; and meansfor extracting melted fat from the target area.

In still another aspect of the invention, a method is provide forinducing skin tightening around regions from which adipose tissue hasbeen removed using the system that includes a solution ofphoto-absorbing nanoparticles; means for injecting the solution into thetarget area; a near infrared light source for delivering a beam of lightto the target area; at least one beam adjusting optical element forcontrolling focus and beam size within the target area; a systemcontroller for providing control signals to the infrared light source,wherein the control signals comprise selection of an emissionwavelength, an emission intensity and an exposure duration, and whereinthe emission wavelength is adapted to excite the nanoparticles to meltfat within the target area; and means for extracting melted fat from thetarget area.

Another aspect of the invention is a photothermal agent for melting fatand skin tightening comprising photo-absorbing nanoparticles suspendedin a solution, wherein the photo-absorbing nanoparticles are adapted toconvert NIR light energy into fat-melting heat in a target area in whichthe nanoparticles have been injected. In a preferred embodiment, thenanoparticles are gold nanorods.

Yet another aspect of the invention is a kit for in vivo photothermalremoval of fat in a target area irradiated by NIR light energy, the kitincluding photo-absorbing nanoparticles suspended in a solution, whereinthe photo-absorbing nanoparticles are adapted to convert NIR lightenergy into heat having a temperature that melts fat; a first syringeadapted for injecting the nanoparticle solution into a target area; anda second syringe or cannula adapted for aspirating melted fat from thetarget area after exposure of the target area to NIR light energy forperiod of time sufficient to melt the fat.

The combination of gold nanorods and NIR light to gentle melt andliquefy adipose and skin has not heretofore been disclosed. Thiscombination offers unparalleled spatial and temporal control that noexisting technique offers. The result is gentle fat melting, and minimalpostoperative pain, by eliminating unnecessary damage to blood vesselsand nerves. It is important to note that many of the prior arttechniques emulsify fat, breaking it down into small globules—they donot melt fat. This has direct implications on how the fat can beremoved. As a result, the inventive technique is expeditious andminimally invasive, eliminating the need to use larger, traumatizingcannulas that are inserted through small incisions. While other priorart methods do melt fat, they do so by heating methods(chromophore-dependent) that present a real risk of thermal damage tothe skin surface and/or tissue surrounding the target site.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary sequence of steps in a procedure forselective fat removal according to the present invention.

FIG. 2 is a diagrammatic view of a kit and apparatus for performingselective fat removal.

FIG. 3A and 3B are plots of wavelength versus absorption, where FIG. 3Ashows absorption in the visible range and FIG. 3B shows absorption withthe visible range removed.

FIG. 4 shows three photographs demonstrating the absence of meltingunder different laser heating conditions.

FIGS. 5A and 5B are photographs of butter samples before and after laserirradiation with and without gold nanorods, respectively.

FIGS. 6A-6B are photographs of bacon fat samples with and without goldnanorods after exposure to NIR laser heating; FIG. 6C is a photograph ofbacon meat without gold nanorods after NIR laser irradiation.

FIG. 7 is a plot of optical density versus wavelength for variousconcentrations of gold nanorods.

FIGS. 8A-8D are micrographs of ex vivo porcine skin and subcutaneoustissue illustrating the histological effects of the inventive procedure.

FIGS. 9A-9C are histograms comparing results of the inventive procedurewith standard suction-assisted lipectomy (SAL), where FIG. 9A showstotal subcutaneous tissue in lipoaspirate, FIG. 9B shows free-acid fattycontent in lipoaspirate, and FIG. 9C shows cell diameter inlipoaspirate. FIG. 9D is a set of dark-field micrographs of tissuefollowing SAL and the inventive procedure.

FIGS. 10A and 10B are representative ultrasound images prior to and 3months post-treatment using the inventive method (FIG. 10A) and SAL(FIG. 10B), with the vertical lines indicating the adipose layertargeted by the procedure. FIG. 10C plots the quantified tissuethickness for the inventive procedure (left) and SAL (right) for 3 pigsbased on 20 measurements per procedure.

DETAILED DESCRIPTION

Disclosed herein are a method and system which combine gold nanorods,near infrared light and minor medical procedures to reduce and removefatty tissue. By injecting a small volume of a solution of gold nanorodsinto the targeted area, the invention provides for the selective meltingof fat and the tightening of skin upon illumination using a low power,biologically benign Near Infrared (NIR) laser.

FIG. 1 illustrates the process flow for the inventive method, with eachprocess step linked by an arrow to a diagrammatic image of the step asperformed on a target area of a patient. The flexibility in the laserdiameter, shape and intensity allows precise control over the targetarea, which may vary from very small, on the order of a few millimeters,to relatively large, e.g., several centimeters in diameter. In step 102,the physician administers a subcutaneous injection into the target areaof a solution of gold nanorods (GNRs) suspended in a sterile, inertliquid, e.g., distilled water, using a fine syringe. In step 104, theGNR solution diffuses through the adipose tissue to be targeted.Immediately after injection, or as soon as practically possible, NIRlaser light is focused onto the target area (step 106) for a period thatmay range from a few seconds to several minutes, depending on the areaand volume of the targeted fat, and at least for a sufficient period oftime to induce surface plasmon resonance within the GNRs. The laserlight has a wavelength within the range of 600 nm to 950 nm, preferablywithin the range of 700 nm to 900 nm, and more preferably about 800 nm.In step 108, SPR is induced, producing localized heating which, in step110, causes the solid fat to liquefy. Finally, in step 112, thephysician inserts a syringe into the targeted area to aspirate theliquefied fat.

A similar procedure may be used to heat and thus stimulate thesurrounding skin to minimize sagging after adipose tissue removal. Insuch a procedure, the GNR solution may be applied directly to the skinor injected intradermally prior to irradiation by the NIR laser light.

FIG. 2 is a representative schematic diagram of the components of thesystem 10 of the present invention. The GNRs 8 (in solution) areinjected into the target tissue 20 using syringe 24. The GNRs arepreferably suitable for in vivo use, for example, a polymer coating canbe added for long circulation. The GNR's should be sterilized andcertified endotoxin-free. The NIR laser energy 6 from the energy source14 is directed into delivery device 16 via a delivery channel 18, whichmay be a fiber optic, articulated arm, or other appropriate opticalwaveguide. In preferred embodiments, the NIR laser is tunable to allowselection of a wavelength that is optimized for different size GNRs. Thelaser should preferably have adjustable power to modulate the degree ofheating. Control system 22 provides a user interface for use by thephysician, or assisting nurse or technician, to select the appropriatelaser wavelength, intensity, duration and other parameters that mayaffect the treatment. At the distal end of delivery device 16 is anenergy directing means 28 for directing the pulsed energy toward thesurface tissue 12 overlying the target tissue (fat) 20. The directingmeans 28 may be one or more optical elements such as a lens or otherfocusing element, beam shaping optics, slits, apertures, gratings, anarray of lenses and other optics or other focusing configuration, whichfocuses the beam within the targeted volume of fat containing the GNRs.In a preferred embodiment, the optical elements may include beamexpanding lenses to allow adjustment of the beam spread to coverdifferent size target areas. Following irradiation of the GNRs in thefatty tissue to liquefy the fat 20, the liquid is aspirated usingsyringe 26 that is inserted into the pocket of liquefied fat. Theinvention further includes a kit for performing selective fat removal inconjunction with an existing NIR laser unit. The kit includes the GNRs 8in solution and syringes 24 and 26. The syringe for extracting theliquefied fat may be replaced by a fine cannula connected to a vacuumsource that is capable of generating suction at the distal end of thecannula sufficient to draw the liquefied fat from the target area andinto a collection vessel.

The inventive technique is possible because NIR light of low power isminimally absorbed by endogenous components in the body, such as skin,water, hemoglobin. Furthermore, low power near infrared light does notcause photodamage to tissue. NIR light is currently used for imagingusing Indocyanine green (ICG), an FDA approved imaging agent able toabsorb and emit in this region. While skin and adipose tissue do notabsorb the NIR wavelengths, GNRs do, enabling fine tuning of thespatiotemporal parameters of heating.

Because the fat is actually liquefied, the inventive method forselective fat removal has the further advantage of being able to useneedles or cannulas that are much smaller in diameter (on the order of16 or 18 gauge) than those required for conventional liposuction, thusreducing patient discomfort, minimizing the risk of damage tosurrounding tissue, reducing the risk of scarring and infection, andaccelerating healing at the site of the procedure. Another majorimprovement over the prior art methods is the duration of treatment. Thehighly selective and rapid heating produced by the excited GNRs iscapable of producing the desired results within minutes, in contrastwith the multiple hours required by typical liposuction procedures.

The following examples demonstrate the principles used in the presentinvention.

EXAMPLE 1 Photothermal Melting of Butter

To demonstrate the selective photothermal melting of fat, we performedexperiments on a ˜2 mm layer of butter sandwiched between two slidesseparated by a silicone spacer small. Gold nanorods (GNRs) were procuredfrom Nanopartz™, specifically “Ntracker™ for in vivo Therapeutics” goldnanorods coated in a proprietary dense layer of hydrophilic polymers,with 10 nm axial diameter and 42 nm length. According to informationprovided by Nanopartz, at this aspect ratio, the plasmon absorptionpeaks are at 817 nm and 512 nm. Laser heating was conducted on buttersamples with and without GNRs using an unfocused (˜2 mm diameter) 800 nmbeam from a Ti-Sapphire (100 fs, 80 MHz) laser. The GNR-butter sampleswere prepared from a mixture of 10 μL of 3×10¹² GNR/mL with ˜50 mg ofbutter. Melting was monitored by visual inspection.

The melting point of butter is 32-38° C. and its specific heat is ˜5joules/g° C. This means that with the ˜2 mm diameter beam at 800 nm at0.45 W power (14 W/cm²), the illuminated butter sample should heat at arate of approximately 2 degrees every second. The input heat andresulting heating rate is likely less in actuality because of absorptionof the microscope slide glass.

The butter sample used in these experiments shows no absorption in theregion of the laser illumination wavelength, 800 nm, as shown in FIGS.3A and 3B. The primary contribution to absorption is the fatty acids inthe milk fat, which absorb in the visible range of the spectrum. Theopacity of the sample limits the transmission of light through thebutter so the optical density is high, as shown in the plot of FIG. 3A.If the contribution of the light scattering to the spectrum is removed,the absorption due to the butter can be better visualized, as shown inFIG. 3B.

Experiments on a plain butter sample showed that melting does not occurafter 3 minutes, shown in the photos of FIG. 4, and up to 10 minutes,shown in FIG. 5A, of illumination with a 0.45 W laser beam.

In the case of the GNR-butter sample under similar experimentalconditions, melting of the butter was observed in the area irradiated bythe NIR laser beam after 2.5 minutes of illumination. FIG. 5B shows thebutter before and after irradiation.

EXAMPLE 2 Photothermal Melting of Meat and Fat

Testing was also performed on bacon samples to compare the heatingbehavior in fat versus meat. We added 10 μL of 3×10¹² GNR/mL in wateronto the fatty sections of the bacon and illuminated the treatedsections with a ˜2mm diameter 800 nm beam at 2.5 W power. Melting of theGNR-injected fat was observed after 45 sec in the volume traversed bythe laser beam where GNRs were present. Illumination was maintained fora total of 1.5 min to further melt the fat and determine whethercharring can occur when high temperatures are attained. As shown in FIG.6A, charring was observed. The melted fat (grease) became so hot that itsplattered around the fat sample, indicated by the arrows in the figure.Control experiments on similarly irradiated non-GNR fat showed nomelting (FIG. 6B). After irradiation, the fat had the same appearance asnon-irradiated samples. The irradiated meat sections without GNRs weresimilarly unaffected (FIG. 6C). These results demonstrate the highlyselective nature of the heating in the GNR-injected areas of fat versusuntreated areas.

Experiments indicate that a GNR solution of within a range of 10¹¹ to10¹³ GNR/mL in water would be an effective injectable photothermal agentfor melting adipose tissue upon irradiation with a NIR laser as aprelude to in-vivo fat removal. A preferred concentration range is onthe order of 2×10¹¹ to 3×10¹². For the removal of 50 mL of fat, lessthan 10 mL of the GNR solution may be required. At the price of around$500 per liter of solution within the stated concentration range, themethod provides an affordable alternative to conventional liposuctionapproaches.

EXAMPLE 3 Ex Vivo Tissue Evaluation

GNR solution was produced, packaged and released in accordance with theFDA's current Good Manufacturing Practice guidelines by NanoSpectraBioSciences, Inc. (Houston, Tex.) following the literature. GNRs (10nm×40 nm) were functionalized with poly(ethylene-glycol) (PEG) (5 kDa)via displacement of hexadecylcetyltrimethylammonium bromide (CTAB), adetergent used in the synthesis of GNRs. Proposed specifications forGNRs in the commercially produced NanoLipo™ system are summarized inTable 1 below.

TABLE 1 Test Procedure Specifications Absorption peak UV/visspectrophotometry  800 ± 10 nm Particle concentration Transmissionelectron  1.6 × 10¹³ NR/ml microscopy (TEM) Optical density UV/visspectrophotometry   50 ± 5 OD at 800 nm Dimensions Transmission electronLength: 40 ± 5 nm microscopy (TEM) Width: 10 ± 2 nm CTAB concentrationISO 2871-2: determination of ≦4 μM cationic-active matter content

As shown by FIG. 7, the optical density of the GNR solution is tunable,ranging from a peak of about 0.5 A.U. for 14 μg of GNR/mL of water to2.5 A.U. for 55 μg of GNR/mL of water. (Note that in the plot, “AuNR/mL”is the same as “GNR/mL”.) The dimensions of the gold nanorods determinethe peak absorption, which at every concentration is around 800 nm. Thedashed line at the bottom of the plot shows the absorbance of water,which does not absorb at 800 nm, and peaks at around 980 nm.

The Lumenis LightSheer® Duet™ laser system (Lumenis, Yokneam, Israel), acommercially available, FDA-approved device with an 800 nm pulsed diode,was used for all studies. In general, in lasers used for cutaneoustreatments, in addition to fluence, the variables that are adjusted tomatch the target are the pulse duration and the spot size. The pulseduration is adjusted to maximize the heating of the target area relativeto surrounding structures, as proposed by the theory of selectivephotothermolysis. The spot size is chosen with multiple criteria: tomatch the size of the treatment area as closely as possible so as tominimize treatment time, and to achieve variable depth. Optimal heatingcan be achieved by altering not only fluence and pulse duration, butalso by adjusting the spot size. It is known that small spot sizesrequire higher fluences to heat targets effectively. The effect of spotsize on the depth of laser penetration is explained at least in part bythe phenomenon of dermal scattering. As a result, as spot sizeincreases, the light penetrates deeper. Consequently, a larger spot sizeallows more effective heating, and conversely deeper heating can beachieved with lower fluences when delivered with a larger spot size.Spot sizes may range from around 9 mm×9 mm to around 35 mm×35 mm.Typical pulse durations can be in the range of around 30 ms to 60 ms,while fluences may range from around 4 J/cm² to 35 J/cm². In the currentstudies, the laser probe had an application area of 3.5 cm×2.2 cm, andwas set to generate three consecutive 30 ms pulses with a fluence of 6J/cm² (46 J/pulse) each pass (i.e., 138 J per pass before accounting forany attenuation by the tissue). In animal studies, the skin was cooledafter a number of passes using a cool or cold compress, e.g., a damptowel or other cooling material, to keep skin surface temperatures below42° C.

Ex vivo studies were performed on food-grade porcine abdominal tissue(pork belly). GNR or saline solution was injected into the experimentaland control areas, respectively. Another region was treated with thelaser only. The experimental and laser-only regions were exposed to 20passes of the Lumenis laser. Frozen sections (10 μm) were stained withhematoxylin and eosin, prior to imaging using a Hamamatsu NanoZoomer2.0HT slide scanning microscope.

Porcine tissue was subcutaneously injected with GNR solution (0.1 g/L)and irradiated with a laser (800 nm, 2.5 kJ total, 30 ms/pulse),injected with GNR solution only, irradiated without GNRs, or leftuntreated as a control. In the absence of GNR solution, histology showedno signs of significant lipolysis (FIGS. 8A and 8C). Skin surfacetemperature was monitored and did not exceed 45° C. in the GNR-treatedsamples. GNR-treated regions appeared more translucent than regionstreated with laser alone, suggesting liquefaction of fat. The tissue wasalso mechanically softer when probed with tweezers. Histology revealeddisruption, apparent as voids, in subcutaneous adipose tissue but not inthe dermal layer or connective tissue of GNR-treated samples (FIGS. 8Band 8D). Disruption of adipose tissue in these samples made themnoticeably more fragile and difficult to section. Dermal and connectivetissues in the GNR-treated samples appeared similar to those ofuntreated samples.

EXAMPLE 4 Pharmacokinetics and Biodistribution of GNRs

Zucker rats were fed an unrestricted diet to maximize body fat content.Abdominal hair on the animals was trimmed using clippers and removedusing a commercial depilatory such as NAIR™ (Church & Dwight Co, Inc.,Ewing, N.J.). Following sterilization with surgical betadine, tworegions were tattooed for conventional SAL or the inventive GNR-basedprocedure. During all procedures, surface skin temperature was monitoredby a FLIR E50 infrared thermal camera.

Lateral subdermal tissue was infused with 1 mL of GNR solution(NanoSpectra solution diluted to 87.5 μg/mL). In one group of rats, theinfused area was subjected to liposuction (SAL or GNR-based); incontrols, no surgical procedure was performed. An untreated baselinegroup was also included. Blood was periodically collected via the tailfor the first 48 hours. Rats were weighed and sacrificed at 24 hours, 48hours, and 30 days post-operation and whole organs (spleen, liver,kidney, heart, lungs, brain, skeletal muscle, lipoaspirate, and treatedregion) were harvested and homogenized using zirconia/silica 2.3 mmdiameter beads.

Gold content was measured in each organ by inductive coupled plasma-massspectrometry (ICP-MS) following tissue dissolution in concentrated HNO₃(67-69%) for five days. Fat-rich tissue required special processing, andwas heated at 65° C. for 3 hours or until the solution became clear,indicating complete digestion. 175 μL of each solution was diluted to 4mL, filtered (0.2 μm pores), and analyzed using a ThermoQuest Element 2high-resolution ICP-MS machine.

PEG-coated GNRs in GNR-solution are essentially innocuous and theinjected dose was below the LD50 of GNRs. The pharmacokinetics andtoxicity of GNRs were examined in Zucker rats by ICP-MS at 24 and 48hour post-subcutaneous injection; the extent of gold removal byliposuction was assessed by comparison to rats in which fat was notremoved following GNR injection. In rats in which no liposuction wasperformed, we immediately observed evidence of gold accumulation in theliver, with approximately the same levels at 24 and 48 hours (7±2%). Inrats treated with liposuction, the amount of gold remaining in alltissues was 34±16% lower than the injected dose. In these rats, thelevel of gold in the liver was very low at 24 h (<5%) but GNRs appearedto redistribute from the treated area to the liver at 48 h, to a levelcomparable to animals with no liposuction. Total recovered gold from allorgans, including tissue removed by liposuction, nearly equaled theamount injected in all cases. In untreated rats, no gold was detected.Furthermore, ICP-MS of organs at 30 days showed that residual gold waspresent at greater levels in the kidneys (2%) than at 24 and 48 h (0%).Rats were weighed weekly to detect any GNR-induced weight loss, whichcould indicate toxicity. No significant weight loss was observed in ratstreated with either the GNR-based procedure or conventional SAL up to 1month.

EXAMPLE 5 Procedure Efficacy in Yucatan Mini Pigs

We next examined whether the inventive procedure enhances fat removalrelative to standard liposuction techniques using Yucatan mini pigs,whose soft tissue structure is more similar than smaller animals' tothat of humans. The pigs were fed a standard diet with three meals perday. Procedures were performed on two abdominal regions on each pig.

Abdominal hair was trimmed using clippers and removed using a commercialdepilatory such as NAIR™ (Church & Dwight Co, Inc., Ewing, N.J.).Following sterilization with surgical betadine, two regions weretattooed for conventional SAL or the inventive GNR-based procedure.During all procedures, surface skin temperature was monitored by a FLIRE50 infrared thermal camera.

GNR solution was mixed with anesthetic tumescent solution (Ringer'ssolution saline with 0.1% lidocaine, 1 ppm epinephrine) to aconcentration of 2.5×10¹¹ GNR/mL (14 μg GNR/mL). 100 mL of the solutionwas injected into adipose tissue through a small stab incision in asystematic fan pattern to ensure uniform permeation and distribution inthe target region (5 cm×5 cm). The laser (spot size ˜2.3 cm×3.5 cm) wasapplied to the marked area over the course of 5±1 min (approximatelytwenty-four passes) to deliver 1000-2000 J of energy, alternating theorientation of the laser application probe to ensure complete coverageof the area. (Note that this is less than the ˜10 minute optimal waittime for lidocaine and epinephrine to take effect before initiatingconventional SAL.) The skin was cooled using a wet towel every fourpasses to maintain a safe skin temperature, as verified by the thermalimaging camera (FLIR E50, FLIR, Wilsonville, Oreg.). Subcutaneous tissuewas removed by suction-assisted liposuction (Gomco OptiVac® G180, AlliedHealthcare Products, St. Louis, Mo.) and the incision was closed usingan absorbable suture, while the operated areas were marked with anon-absorbable suture.

Lipoaspirates were centrifuged at 1000 rpm for 5 min to separate theliquid phase, including injection solution, from solid subcutaneoustissue. Both phases were weighed, and subcutaneous tissue was examinedunder dark field microscopy at 10× magnification. Cell diameters (alongthe longest axis, all cells in each field of three representativeimages, totaling ˜50 cells) were measured using ImageJ software. Toquantify the proportion of removed subcutaneous tissue consisting offree fatty acids and glycerol, 1 g of each subcutaneous tissue samplewas digested with 3 mg collagenase/dispase following manufacturerprotocol for 1 hour at 37° C. (Roche) and centrifuged (2000 rpm, 5 min)to produce three distinct layers (from top to bottom: free fatty acidsand glycerol, adipocytes, and fibrous matter). The percentage of removedtissue consisting of free fatty acids and glycerol was determined bymeasuring the volume of the upper layer containing secreted fatty acidsand glycerol, converting it to mass (assuming 1 mL=1 g), and dividing bythe total mass of removed tissue.

Ultrasound measurements were taken using a Biosound MyLab30Vet machinewith a LA435 Linear Probe 18-10 MHz transducer through a thick layer ofultrasound gel before, immediately after, and at 10 days, one month, twomonths, and three months post-procedure to monitor changes in tissuedepth. User pressure did not affect measurements of adipose layerthickness, as no significant difference was detected betweenmeasurements collected at maximum (gentle) pressure and the moment justbefore the transducer detached from the surface following release ofpressure. Additionally, images were acquired during exhalation toaccount for any changes in depth due to breathing. Images parallel andperpendicular to the spinal axis of the animal were acquired to obtaincomplete coverage of the operated area. The machine was set to measurethe same depth for all time points for each region.

In each image, the distance from the top of the deep fascial membrane tothe top of the superficial fascial membrane, which appears white onultrasound, was measured at four cross-sections spaced 1 cm apart ineach ultrasound image (five images per treated region) using ImageJ.Images in which resolution was too low to identify fascial membranes(fewer than 10% of images) were not analyzed. Each measured distance isplotted to illustrate the change in average depth over time.Interpretation of ultrasound was aided by compression testing duringimage collection; fat layers compressed more than fibrous layers.

Skin appearance was assessed by ruler measurement and photography.Continuous variables, except for adipose thickness measured byultrasound, are reported as means and standard errors. Groups werecompared by two-tailed student's t-test in Microsoft Excel 2010.

The inventive GNR-based technique, also known as “NanoLipo™”, allowedremoval of considerably more subcutaneous tissue (FIG. 9A) and fat thanconventional SAL in a comparable amount of time. Further, the NanoLipo™procedure required much less time (4 min vs. 10 min) to remove a similarvolume of lipoaspirate while causing less bruising than SAL. Collagenasedigestion and centrifugation revealed that the fatty content of tissueremoved following the NanoLipo™ procedure was nearly twice thatfollowing SAL (FIG. 9B). As photothermolysis may trigger release offatty acids and glycerol from adipocytes, which would reduce theirdiameter, we compared the diameter of adipocytes in lipoaspiratesfollowing each procedure by dark field microscopy and image analysisusing ImageJ software. Adipocytes in lipoaspirates following NanoLipo™treatment were significantly smaller than those in lipoaspiratesfollowing SAL, as shown in FIG. 9C. The dark field micrographs of FIG.9D further illustrate the difference in the average diameter ofadipocytes for the GNR-based and conventional SAL procedures.

Example 6 Assessment of Tissue Depth Using Ultrasound

To assess whether the NanoLipo™ procedure enhances reductions in adiposetissue thickness and yields more uniform results relative toconventional SAL, we measured the thickness of the superficial adiposelayer before and immediately after the procedure, as well as at 1, 2,and 3 months post-operation using ultrasound. The resulting images areshown in FIGS. 10A and 10B for the GNR-based procedure and SAL,respectively. Analysis of ultrasound images reveals comparable depthchanges between the NanoLipo™ treatment and SAL immediatelypost-operation. FIG. 10C plots the quantification of tissue thicknessfor three separate procedures, NanoLipo™ (left) and SAL (right),performed on three pigs, with 20 measurements per procedure. Theseresults correlate well with the total volume of subcutaneous tissueremoved, shown in FIG. 9A. The change in superficial adipose thicknessat one month post-surgery is significant in NanoLipo™ method treatedareas but not in those treated using SAL, suggesting that either lessswelling occurs, or that swelling subsides faster, with localizedthermally-aided fat removal. While we cannot compare adipose tissuethickness across surgical procedures because of differences innormalization, the inventive GNR-based technique appears to providegreater reductions in thickness at 3 months post-surgery, as evidencedby FIGS. 10A and 10B. Tissue depth reduction is more uniform inNanoLipo™-treated regions than in those treated with SAL across all timepoints, as evidenced by a tighter distribution of thicknesses shown inFIG. 10C.

The application of the inventive technology has many secondary benefitsin addition to the cosmetic effect of eliminating body fat. For example,illnesses such as diabetes mellitus are directly related to fat storageand obesity. Insulin resistance can be eliminated by reducing body fatcontent. This scientific fact has significant implications on chronicillnesses such as diabetic nephropathy, diabetic retinopathy andcoronary heart disease. To date, existing techniques have not exhibitedthe ability to remove an effective amount of fatty tissue withoutcausing severe damage to adjacent tissue. In addition, during existingprocedures, patients are exposed to the potentially dangerous effects oflidocaine toxicity, which is included in current tumescent solutions.

The controlled thermal melting of fat protects all other vitalstructures, reducing post operative pain and, hence, reducing the amountof lidocaine needed in a tumescent solution and avoid life-threateningrisks of lidocaine toxicity. The fact that no-to-minimal mechanicalforce is required to practice the inventive technique further eliminatesthe risk of penetrating deep tissues. Penetration of tissues such asbowels, livers and lungs has been reported in the literature with use ofexcessive force to achieve adequate liposuction.

Selecting an appropriate laser pulse length, among other parameters,allows the inventive GNR-based procedure to precisely increase theamount of energy conveyed to the target, i.e., adipose tissue. The majoradvantage of this technology is a consequence of the addition ofexogenous energy absorbers (GNRs) rather than relying on endogenouselements, such as water. Test results strongly suggest that theNanoLipo™ procedure aids in removal of adipose tissue while maintainingthe integrity of surrounding tissues. Although the inventive approachinvolves an additional laser step compared to SAL, in SAL the surgeonmust wait 10 min for the tumescent solution to take effect. Because thelaser can already be applied during this period, the GNR-based approachrequires no more time than SAL. Importantly, the NanoLipo™ techniqueaccelerates fat removal during the liposuctioning step because ofphotothermal fat melting.

In addition, since GNRs do not bind to tissue, a large portion ofinjected GNRs are immediately removed by aspiration. Since theconcentrations delivered (0.01-0.05 g/kg body weight) are well below theexpected toxicity limit (3.2 g/kg) for gold, long-term GNR exposure isnot expected. In combination with the temporary nature of the mechanicalchanges induced by selective photothermolysis, the NanoLipo™ procedureshould be well-tolerated.

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1.-28. (canceled)
 29. A method for selective removal of fat from atarget area in a subject in need thereof, comprising: distributingphoto-absorbing nanoparticles uniformly within a target area comprisingadipose tissue located beneath a skin surface by injecting a solutioncomprising gold nanorods suspended in a biocompatible liquid at aconcentration range of 10¹¹ to 10¹³ GNR/mL; and delivering a series ofpulses of near infrared light across the skin surface and into thetarget area for an exposure duration to induce surface plasmon resonancein the nanoparticles, wherein the near infrared light has a combinationof optical parameters selected from the group consisting of beam energy,pulse duration, emission wavelength within a range of 700 to 900 nm,emission intensity, beam focus and beam area, the optical parameters andthe exposure duration selected to excite the nanoparticles to liquefyfat within the target area.
 30. The method of claim 29, wherein the stepof delivering comprises scanning the near infrared light across thetarget area using a plurality of passes.
 31. The method of claim 29,further comprising, after the step of delivering, applying a coolingmaterial to the skin surface.
 32. The method of claim 29, wherein theemission wavelength is 800 nm ±10 nm.
 33. The method of claim 29,wherein the gold nanorods have an aspect ratio in the range of 1:3-1:5.34. The method of claim 29, wherein the gold nanorods have an axialdiameter of approximately 10 nm and a longitudinal diameter in the rangeof 9 to 50 nm.
 35. The method of claim 29, wherein the gold nanorodshave a length of 40±5 nm and a width of 10±5nm.
 36. The method of claim29, wherein the biocompatible liquid comprises water and an anesthetictumescent solution.
 37. The method of claim 29, wherein the beam energyis in a range of 1000 to 2000 J.
 38. The method of claim 29, wherein thepulse duration is within a range of 30 ms to 60 ms.
 39. A method forsubcutaneous fat removal and skin tightening in a person in needthereof, the method comprising: subcutaneously injecting a suspension ofphoto-absorbing gold nanorods in solution into a target region ofadipose tissue of the person, wherein the nanorods have an aspect ratioin the range of 1:3 to 1:5; and scanning pulses of NIR light energy fora plurality of passes across a skin surface overlying the target regionand into the injected suspension for an exposure duration, the NIR lightenergy having optical parameters selected from the group consisting ofbeam energy, pulse duration, emission wavelength within a range of 700to 900 nm, emission intensity, beam focus and beam area, the opticalparameters and the exposure duration selected to excite thenanoparticles to liquefy fat within the target region.
 40. The method ofclaim 39, further comprises applying a cooling material to the skinsurface after a subset of the plurality of passes.
 41. The method ofclaim 39, wherein the emission wavelength is 800 nm±10 nm.
 42. Themethod of claim 39, wherein the gold nanorods have an axial diameter ofapproximately 10 nm and a longitudinal diameter in the range of 9 to 50nm.
 43. The method of claim 39, wherein the gold nanorods have a lengthof 40±5 nm and a width of 10±5 nm.
 44. The method of claim 39, whereinthe suspension has a concentration of 10¹¹ to 10¹³ GNR/mL in water. 45.The method of claim 39, wherein the suspension further comprises ananesthetic tumescent solution.
 46. The method of claim 39, wherein thebeam area is within a range of 9 mm×9 mm to 35 mm×35 mm.
 47. The methodof claim 39, wherein the beam energy is in a range of 1000 to 2000 J.48. The method of claim 39, wherein the pulse duration is within a rangeof 30 ms to 60 ms.